The invention concerns an electricity meter and an input module for an electricity meter.
The invention concerns an electricity meter as set forth in the classifying portion of claim 1 and an input module for an electricity meter, as set forth in the classifying portion of claim 10.
CH 687 423 A5 discloses an electricity meter, in particular a multi-function meter, in which a respective measuring unit is provided for each phase. Current and voltage of the respective phase are fed to the respective measuring units. Each measuring unit generates output pulses of a frequency which is proportional to the power value consumed in the phase in question. In accordance with one embodiment, the measuring units can be connected at the output side to a microcomputer by way of a bus structure. The measuring units each preferably have as the current sensor a Hall element with a voltage frequency converter connected on the output side thereof. The bus connection is preferably in the form of a standardised bidirectional bus connection, while the measuring units can also supply digitised instantaneous values of the associated phase load current and the associated phase voltage. Processing of the recorded measurement values is then firstly effected in the downstream-connected microcomputer. It is optionally also possible to arrange downstream thereof a further processing arrangement with CPU/processor and associated memories. Admittedly, those meters involve digital measurement value processing, but a specific or separate analog/digital converter is not used.
U.S. Pat. No. 5,349,676 discloses a digital electricity meter in which a respective xcexa3xcex94-modulator is provided as an analog/digital converter (A/D converter) for each measurement value to be detected (current or voltage). The digitised measurement values are then processed by means of two processors. The entire signal processing arrangement including A/D-converter, processors, memories and so forth are disposed on a common IC.
A similar arrangement is known from U.S. Pat. No. 5,544,089 and U.S. Pat. No. 5,631,843. In that case also A/D-converter, filter, memory and at least one processor are disposed on a common chip. The design configurations in the two publications last referred to suffer from the disadvantage that they only use special ICs which, by virtue of their high integration density, are expensive and are only directed to specific applications. Further digital electricity meters are known from DE 195 26 723 C1 and EP 0 887 650.
The object of the present invention is to provide an electricity meter and an input module which is suitable for same, wherein, starting from the use of standard processing modules and components, optimum integration is to be implemented in terms of pre-processing and detection of the input signals.
Accordingly, taking the state of the art as the basic starting point, it is provided in accordance with the invention that the input module is in the form of a separate integrated circuit which is separate from the processing module and that provided as the multiplying means is a hardware multiplier which is integrated into the integrated circuit. Preferably the A/D converter is in the form of a sigma-delta-modulator (xcexa3xcex94-modulator) which is integrated into the integrated circuit.
That simple design configuration affords a modular structure for an electricity meter, wherein processor or computing modules which are available as standard can be used for digital data processing. By virtue of the simple design configuration of the input module, it can be produced inexpensively, in large numbers of items, whereby overall the electricity meter can be produced at low cost and with a low level of complication.
It is desirable if the input module has multiplying means for forming a power value. In that case, the multiplying means can advantageously be in the form of a hardware multiplier which is integrated into the integrated circuit. That avoids time-consuming computing procedures in the downstream-disposed processing module. The simplest case only involves providing for accumulation of the power values supplied by the hardware multiplier, in order to arrive at an energy consumption value.
Preferably, an input module is to be provided for each phase, in particular for three phases, of a consumer or the network to be connected to the electricity meter. The modular nature of the input portion of the electricity meter thus affords simple adaptation to the required number of phases. It is also possible to provide a multiplicity of input modules, which multiplicity is subdivided into groups, with each group being associated with a respective consumer. In that way it is in effect possible to put together a multiple measuring arrangement, in which case the energy consumptions of different consumers or loads can be detected by means of a central processing arrangement.
It is desirable if a current sensor which includes at least one Hall element is provided for each input module. A current sensor of that kind can be easily integrated into the input module, with the amount of space required being small. It will be appreciated that alternatively it is also possible to use other kinds of current sensors, for example a field sensor, a magnetoresistive bridge, a sensor with shunt or a conventional current converter on a magnetic basis.
Preferably the connection between the input module or modules and the processing module is in the form of a bus connection, in which case for that purpose each input module has a bus coupler or interface module. In that way it is possible to provide for fast data transfer from the input module or modules to the processing module, which permits a high rate of data throughput with a high level of resolution. In that case data transfer can take place in parallel or serial mode.
A respective A/D converter can advantageously be provided for the analog current input and the analog voltage input. That affords separate signal processing in which mutual influencing is kept at a low level.
Alternatively, it is also possible to provide a common A/D converter with a multiplexer connected on the upstream side thereof. A design configuration of that kind can be easily implemented, with only a slight amount of circuitry expenditure and complication being required within the integrated circuit. In this embodiment, cross-talk is prevented between the channels for current and voltage, in comparison with an arrangement having two A/D converters.
It is desirable if each input module includes a memory in which parameters and/or operating settings and/or other data which can be set or which can be predetermined for operation are or can be stored. That means that a minimum of items of operating information can be stored in the processing module. For that purpose, it is possible to store separately for each processing module parameters which for example are already stored during manufacture and to which access may be made during operation in the installed condition. That concerns for example pre-settings or items of compensating information. There is therefore no need to load the memory resources of the processing module.
In accordance with the invention the object in regard to the input module is attained by a single-phase input module for an electricity meter that is in the form of an integrated circuit. The advantages set forth hereinbefore apply accordingly here. Input modules of that kind are suitable in particular for use in domestic meters or three-phase, of a single-phase or three-phase type.